[Apache POI] xlsx 파일을 xls 파일로 변환하는 메서드

나는 check box와 같은 Excel FormControl 까지 변환하기를 원했는데, 다음과 같은 코드로는 Form Control들까지 복사되지 않는다.

[출처] http://stackoverflow.com/questions/20049922/java-poi-api-convert-from-xlsx-to-xls

/**
 * xlsx 파일(XSSFWorkbook)을 xls 파일(HSSFWorkbook)로 변환하는 메서드.
 * [참조] http://stackoverflow.com/questions/20049922/java-poi-api-convert-from-xlsx-to-xls
 *
 * @param xssfWorkbook
 * @return
 */
private HSSFWorkbook convertXlsxToXls(XSSFWorkbook xssfWorkbook) {

	HSSFWorkbook hssfWorkbook = new HSSFWorkbook();

	int sheetCnt = xssfWorkbook.getNumberOfSheets();
	for (int i = 0; i < sheetCnt; i++) {
		Sheet sIn = xssfWorkbook.getSheetAt(i);
		Sheet sOut = hssfWorkbook.createSheet(sIn.getSheetName());
		Iterator rowIt = sIn.rowIterator();
		while (rowIt.hasNext()) {
			Row rowIn = rowIt.next();
			Row rowOut = sOut.createRow(rowIn.getRowNum());

			Iterator cellIt = rowIn.cellIterator();
			while (cellIt.hasNext()) {
				Cell cellIn = cellIt.next();
				Cell cellOut = rowOut.createCell(cellIn.getColumnIndex(), cellIn.getCellType());

				switch (cellIn.getCellType()) {
				case Cell.CELL_TYPE_BLANK: break;

				case Cell.CELL_TYPE_BOOLEAN:
					cellOut.setCellValue(cellIn.getBooleanCellValue());
					break;

				case Cell.CELL_TYPE_ERROR:
					cellOut.setCellValue(cellIn.getErrorCellValue());
					break;

				case Cell.CELL_TYPE_FORMULA:
					cellOut.setCellFormula(cellIn.getCellFormula());
					break;

				case Cell.CELL_TYPE_NUMERIC:
					cellOut.setCellValue(cellIn.getNumericCellValue());
					break;

				case Cell.CELL_TYPE_STRING:
					cellOut.setCellValue(cellIn.getStringCellValue());
					break;
				}

				CellStyle styleIn = cellIn.getCellStyle();
				CellStyle styleOut = cellOut.getCellStyle();
				styleOut.setDataFormat(styleIn.getDataFormat());

				cellOut.setCellComment(cellIn.getCellComment());

			}
		}
	}
	return hssfWorkbook;
}

[참조] http://notpeelbean.tistory.com/entry/JSP-%EC%97%91%EC%85%80-%ED%8C%8C%EC%9D%BC-%EB%B3%80%ED%99%98-XLSX-XLS-XLS-XLSX-JSP-Page-Only

위 웹페이지에 다음과 같은

getOutputStream() has already been called for this response

에러 해결책이 나와 있는데, 이렇게 하면 되는구나. 흥미롭다.

        out.clear(); //out--> jsp자체 객체

        out=pageContext.pushBody(); //out--> jsp자체 객체

         //getOutputStream() has already been called for this response

         //오류 해결을 위판 편법       

        ServletOutputStream sout = response.getOutputStream();              

        newWb.write(sout);